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There are Two Kinds of Vias in PCB: Blind Via and Buried Via

Blind Via

Blind via is the electroplating hole to connect the outermost circuit in PCB with the adjacent inner layer. It is called blind via because the opposite side cannot be seen. At the same time, in order to increase the space utilization between PCB layers, blind vias are applied. A blind via is a through hole which connects the surface of the printed circuit board.

Features: The blind via is located on the top and bottom surface of the circuit board, and has a certain depth. It is used to link the surface circuit and the inner circuit below. The depth of the hole usually does not exceed a certain ratio (aperture). In this way, special attention should be paid to the drilling depth (Z axis). If not, electroplating in the hole will be difficult. Therefore, it is almost not used by factories. When the circuit layers need to be connected in advance, the holes can be drilled first and then bonded together. However, precise positioning and alignment devices are required.

Buried Via

It refers to the connection between any circuit layers in inner buried-via PCB, but it is not connected to the outer layer, and it also means that the through hole does not extend to the surface of the circuit board.

Features: in this process, it is impossible to drill holes after bonding. Drilling must be carried out at the time of individual circuit layers. The inner layer must be partially bonded and then electroplated. Finally, all the bonding can be achieved. It takes more time than the original through hole and blind via, so the price of buried via is the most expensive. This process is usually only used for high density circuit boards to increase the usable space of other circuit layers.

In PCB production process, drilling is very important. Because drilling is to drill the required through hole on the copper clad laminate to provide electrical connection and fixed device function. If the operation is not proper, there will be problems in the via process. If the device cannot be fixed on the circuit board, the light will affect the use, and the whole board will be scrapped. Therefore, the drilling process is very important.

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